1. Field of the Invention
The present invention relates to an illegal-sheet-material detecting apparatus, which is adapted to detect whether the property of each of the passing sheet materials is legal or not in a sheet manufacturing machine, which places a plurality of sheet materials, each having almost the same property i.e. the presence, etc. of shape, size and printing, such as bill, ballot ticket for election, etc. at intervals for each of the single sheet materials to sequentially pass them through a given position.
2. Description of the Prior Art
A conventional prior art illegal-sheet-material detection apparatus is shown in FIG. 1. In FIG. 1 light-emitting elements 1a and 1b are disposed, respectively, opposite to light-receiving elements 2a and 2b. A sheet material 3 is passed, between them, in the direction of an arrow by a proper means in a known manner. The output signals of the light-receiving elements 2a and 2b at that time are amplified respectively by amplification circuits 4 and 5. Thereafter, the outputs of the amplification circuits 4 and 5 are inputted to a counting circuit 6 which counts the number of the sheet materials 3 and displays the count on a display means 7. The outputs of the amplification circuits 4 and 5 are inputted to a double-feed detection circuit 8 of such character as shown in FIG. 2, to a length-illegality detection circuit 9 of such character as shown in FIG. 3 and to a half-ticket detection circuit 10. When each of these circuits has detected the double feed of the sheet material 3, the length illegality caused due to chain feed, etc., or the half-ticket condition caused due to broken or folded sheet materials, by then the output of the amplification circuit 4 or the amplification circuit 5, a driving circuit 12 causes any additional feeding of the sheet material 3 to stop.
An operation switch 13 outputs, to the control circuit 11, command signals such as start, stop, etc. for the count sheet-number of the sheet materials 3, the count operation.
As shown in FIG. 2, the double-feed detection circuit 8 is provided with a reference voltage producing circuit 21 for setting a reference voltage to be outputted by manual adjustment, a comparison circuit 22 for outputting a signal having a pulse width, which is equal to a period of time during which the size of the difference, with respect to the reference voltage, of the output signal of the amplification circuit 4 becomes larger than the predetermined value, a comparison circuit 23 for outputting the same signal as described hereinabove by the size of the difference, with respect to the reference voltage, of the output signal of the amplification circuit 5, a pulse-width discrimination circuit 24 for discriminating the pulse width of the output signal of the comparison circuits 22, 23. When the double feed of the sheet materials 3 is caused, the time taken for the output signal of the amplification circuit 4 or 5 to exceed the range of the lag with respect to the reference voltage, to be outputted from the reference voltage producing circuit 21 determined by the manual adjustment, becomes longer than the predetermined time. The double-feed detection circuit uses this fact to output the double feed signal from the pulse-width discriminating circuit 24.
As shown in FIG. 3, the length-illegality detection circuit 9 is provided with a passage deciding circuit 25 for deciding whether or not the sheet material 3 has passed between light-emitting elements 1a, 1b and light-receiving elements 2a, 2b, a long-limit timer circuit 26 and a short-limit timer circuit 27 for manually setting the top limit value and the bottom limit value of the time required for the sheet material 3 to pass between the light-emitting elements 1a, 1b and the light receiving elements 2a, 2b a comparison circuit 28 for deciding whether or not the output time of the passage deciding circuit 25 stays between the top limit value and the bottom limit value. When the illegal length is caused by the chain feed, break or the like of the sheet materials 3, the output time of the output signal from the passage deciding circuit 25 becomes larger than the top limit value or smaller than the bottom value. The length-illegality detection circuit uses this fact to output the length-illegality signal from the comparison circuit 28.
However, when the double-feed detection circuit 8 and the length-illegality detection circuit 9 have been constructed, respectively, as shown in FIG. 2 and FIG. 3, the manual adjustment of the reference-voltage producing circuit 21, the long-limit timer circuit 26 and the shortlimit timer circuit 27 is required to be performed again everytime the thickness and size of the sheet material 3 vary. In addition, the double-feed deciding circuit 8 takes its error action due to the drifts, etc. of the light-emitting elements 1a, 1b, the light-receiving elements 2a, 2b and the amplification circuits 4, 5. The length-illegality detection circuit 9 takes its error action due to changes in the feed speed of the sheet material 3.
Also, to remove the above problems, expensive components, which are less in drift with respect to temperature, time lapse, are required to be used for the light-emitting elements 1a, 1b, the light-receiving elements 2a, 2b and the amplification circuits 4, 5, thus resulting in higher cost.